Some methods for locating an object are known in the art. A missing vehicle locator system is described in U.S. Pat. No. 5,418,537 issued to Bird. The vehicle locator system uses one or more GPS systems in conjunction with a GPS antenna, a receiver/transmitter, a telephone with associated antennas, and a modem mounted in a vehicle whose position is to be monitored. A paging request is issued and received by a paging responder in the vehicle. The paging request causes the modem to interrogate the GPS receiver to determine the current position of the vehicle. The current position of the vehicle is transmitted via a cellular telephone link to notify a vehicle location service center of the current location of the vehicle. Other known location determination techniques include the use of a Loran or a Glonass satellite based system.
Another object location system is described in U.S. Pat. No. 5,576,716 to Sadler for locating lost or stolen property. This location system includes a GPS module, a microcomputer, a modem, and a telephone, all of which must be installed in the vehicle. The system described regularly and automatically computes the position of the property for transmission via the phone link to a central receiver/transmission station.
The present applicant has developed various technologies related to communications between locators and transponders as is described in the following issued U.S. patents and published U.S. patent applications: U.S. Pat. No. 7,791,470, titled “SPIN AROUND DIRECTION AND DISTANCE LOCATOR,” and issued on Sep. 7, 2010; U.S. Pat. No. 7,646,330 “SYSTEM AND METHOD FOR LOCATING OBJECTS AND COMMUNICATING WITH THE SAME,” and issued on Jan. 12, 2010; U.S. Pat. No. 7,592,918, titled “ELECTRONIC FENCE MODE ALERT SYSTEM AND METHOD,” and issued on Sep. 22, 2009; U.S. Pat. No. 7,573,381, titled “REVERSE LOCATOR,” and issued on Aug. 11, 2009; U.S. Published Application 2010/0066531, titled “LOCATOR INVENTORY SYSTEM,” and filed on Sep. 12, 2009 as U.S. patent application Ser. No. 12/210,115; U.S. Published Application 2009/0201152, titled “ANTI-TAMPER CARGO CONTAINER LOCATOR SYSTEM,” and filed on Nov. 26, 2008 as U.S. patent application Ser. No. 12/324,615; and U.S. Published Application 2008/0102859, titled “LOCATION OF COOPERATIVE TAGS WITH PERSONAL ELECTRONIC DEVICE,” filed on Oct. 25, 2007 as U.S. patent application Ser. No. 11/924,553.